1. Technical Field
This invention relates generally to a process for producing useful fibers from tropical fiber waste products for ultimate use in connection with a variety of applications, such as the absorption of liquids, paper, textiles, insulation and general fiber filler. The invention also relates to an apparatus for producing the useful fibers.
2. Description of the Prior Art
Presently, banana stalks, plantain stalks, Cavendish plant stalks, pineapple crowns, palm, palmetto and coconut fronds, as well as a variety of other fibrous tropical plant materials are thought of as waste agricultural byproducts in the countries in which they are produced. Currently these byproducts are usually disposed of in landfills, where they can attract insects and contribute to landfill capacity problems. Additionally, they may be discarded into rivers, where they oxidize and can cause potential environmental problems. In other instances, the byproducts are left on the ground to act as a natural fertilizer. Clearly, it would be desirable to convert these plant byproducts into useful fibers rather than allowing them to contaminate the environment.
Generally, these plant materials have a water and natural latex content of as much as 80% by weight, including a variety of resinous or gummy substances. In order to produce workable fibers which have characteristics desirable for use in liquid absorbent applications, textiles, paper-making and insulation, it is necessary to extract these fluids and, in particular, wash out or extract the latex and other natural resinous substances.
Several methods of processing these fibers have been previously developed. However, each suffers from its own drawbacks.
For example, U.S. Pat. No. 1,181,553 to Taylor et al. discloses a process for manufacturing paper pulp from waste by-products of banana plantations, including the steps of: crushing and squeezing the banana plant to break down the fiber and to extract water and natural plant juices; brushing or carding to further separate the fibers; drying and cutting the fibers to the desired length; boiling the fibers in alkali to further clean them and remove resinous or gummy material; and optionally bleaching the fibers if a white paper pulp is desired. However, a shortcoming of this process is that Taylor removes approximately 90% of the natural liquids and resinous material, in large part, by boiling the fibers in an alkaline solution which is likely to damage the fibers and is unnecessarily energy intensive.
Likewise, U.S. Pat. No. 4,547,263 to Quame discloses a process and apparatus for recovering useful products from green plantain stem, including paper pulp. The process of Quame includes the steps of cutting or shredding the raw plant materials; pressing the stems to extract excess liquids; beating the de-liquefied stems; squeezing the resulting slurry; removing pith cells from the fibers; steam cooking the fibers; and bleaching the fibers. The invention of Quame is complex and requires the use of a variety of potentially environmentally damaging reagents including various acids, bases and bleaches. Furthermore, several of the steps described by Quame involve use of steam, which may damage the fibers and is an unnecessarily energy intensive process.
U.S. Pat. No. 1,981,883 to Tappan describes a process for converting banana stalks into paper fibers including cleaning, splitting and de-coring the stalks, crushing the stalks, separating the fibers, drying the fibers and packaging the fibers. Tappan specifies the juices from the banana stalks extracted by the crushing step may be collected and may themselves constitute a useful by-product. Importantly, the process of Tappan does not include any step wherein the fibers are washed or the latex and other resinous substances are extracted, and hence this process is likely to produce dirty fibers with less than desirable fiber characteristics.
A novel approach to this problem is described by Moody in U.S. Pat. No. 1,357,850, which describes a process for obtaining useful fibers from banana stalks and other similar tropical vegetation by immersion of the raw plant materials in electrolyzed brine. The electrolyzed brine solution disintegrates the bulk material, separating the fibers while simultaneously bleaching them. While this process does not involve the use of any environmentally damaging reagents, it is very energy intensive and does not produce a very high quality material.
A number of other processes have been described which rely on boiling in various chemical solutions to extract the resinous material or digest the solid materials associated with the fibers. Processes have been described using aqueous solutions of zinc sulfate and oil (see U.S. Pat. No. 1,362,723 to Marr), sodium nitrate (see U.S. Pat. No. 1,717,798 to Marr) and various alkali solutions. All of these processes rely on the use of potentially environmentally damaging reagents which may introduce associated disposal problems.
As should be readily understood, none of these processes have been optimized to provide a high fiber quality while minimizing the impact of the processing steps on the surrounding environment, both in terms of chemical waste and energy usage.